PLANT TISSUES Lesson Description In this lesson we:  

Identify the different types of plant tissue Be able to relate the different structures with the different functions

Summary Plant Tissue

12 MARCH 2014

TISSUE Meristematic

Epidermis

LOCATION  Apical – tips of roots and shoots  Lateral – sides of roots and stems  Vascular cambium – between xylem and phloem of dicots  Cork cambium – inside cork cells Outer covering of roots, stems and leaves

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Forms bulk of roots, stems, leaves and flowers.

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Chlorenchyma

 In upper layers of leaves and stems  Palisade and spongy mesophyll of leaves

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 Collenchyma

 In epidermis of young stems

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Parenchyma

STRUCTURE Thin willed Large nucleus No intercellular spaces Regular shape

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Stems and leaves  Guard cells surrounding a stoma  Regular shape  Thin walled  No chloroplasts  No air spaces  Covered with a cuticle Roots  Regular shape  No cuticle  Outgrows – root hairs Irregularly shaped round, oval Thin-walled, large vacuole Large intercellular spaces Lack chloroplasts Parenchyma tissue with chloroplasts Thin-walled, irregularly shaped with intercellular spaces. Elongated upper layer – palisade layer Regular shape No intercellular spaces Corners of cells are thickened

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FUNCTION Actively dividing – Mitosis Produce new cells for  Growth in length and width  Replace worn-out or damaged tissue Differentiate into different types of tissue Protect deeper-lying tissue Cuticle reduced loss of water vapour by transpiration Guard cells control opening and closing of stoma, control loss of water vapour and gas exchange. In roots help to absorb water from soil.

Packing tissue Stores food as starch or sugars Intercellular airspaces allow water and gases to pass through. Manufactures food y photosynthesis.

Give support and strength to aboveground parts

Sclerenchyma

Xylem

 Fibres  In epidermis or stems  Cap around vascular bundles of dicot stems  Sheath completely around vascular bundle of monocots  Stone cells in shells of nuts and hard parts of fruits Within veins of leaves, vascular bundles of stems and stele of roots

 Fibres  Long with tapered ends  Thick- walled  Very small inner cavities  Stone cells  Small, oval, irregular cells  Extremely thick walls with lumens almost completely blocked.

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Give mechanical support to plant.

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Vessels and tracheids transport water and mineral salts from roots to stems and leaves Give strength and support

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 Phloem

Within veins of leaves, vascular bundles of stems and stele of roots

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Vessels  Cylindrical cells  Cross walls perforated or absent  No cell contents – dead cells  Form continuous tubes from roots to leaves  Thick walls (lignin)  Lignin laid down to form patterns Tracheids  Ends tapered  Have perforated cross walls Fibres and parenchyma as described above. Sieve tubes  Cylindrical cells  Cross walls perforated to form sieve plates  Thin-walled cells  Contain strands of cytoplasm continuous with that of next cell  Living cells Companion cells  Lie next to sieve tubes  Thin walled with well defined nucleus  Cross wall present Fibres and parenchyma as described above.

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Sieve tubes transport manufactures food from leaves to all parts of body Companion cells probably control the activities of sieve tubes.

Diagrams Parenchyma

Epidermal

Epidermal Tissue – Root Hair

Epide